It depends on what your reason for saying it is. I would not use the word real, I would use the term biological. Real has huge implications.
He may not be your biological dad , but if he has raised you, nurtured you and loved you, he is your dad.
As a stepfather, I dread that phrase, used as a weapon. I know I'm not your Dad, just treat me like an adult (teacher, coach,a stranger) with the same respect you afford those people. My 5 step kids rarely ever say it to my face, but I hear the complaints they register with my wife. While rare, it happens, and I understand its tough to be 16, but I'm all you got, and I'm infinitely nicer than most step dads, and probably easier on the discipline than the real dad would have been.
As an abused chiuld by my step dad you have every right to tell him he is not yourr Father, but if he was around before you got out of diapers he is your dad. Any male can father a child but those who stick aound to ensure you have the needs to grow up met are your dad.
Biology doesn't make you a father. If he has raised, fed, clothed, supported and protected you just the way a father does...then he is your father.
theres a difference between a "Dad" and a "Biological Dad".. there's also a difference between a "Dad" and a "step father"... It depends on how long the "stepfather" has been around for... If he has been around for more than half your life (or longer than your "Dad" was)... You don't get that right....NO. If he hasn't been ... Go Hard...
the fact you're asking means you care